Date: Monday 28-Jan-2008
Speaker: Dr. Frederic Galliano (Univ. of Maryland)
Title: "Dust Evolution in Galaxies"
I will present the results of several studies aimed at understanding the evolution of the PAH and dust properties, as a function of both the environmental conditions and the metal enrichment of the system. I will first discuss the detailed variations of the mid-IR aromatic features through Galactic regions and nearby galaxies, and how these features can be related to the physical conditions. I will show how models of photodissociation regions can be used to investigate this subject. Then, I will discuss the long term evolution of dust in galaxies, comparing the grain production by various stellar progenitors to their destruction by SN blast waves and in HII regions.
Date: Monday 4-feb-2008
Speaker: Prof. Eve Ostriker (Univ. of Maryland)
Title: An Overview of "Theory of Star Formation" - Part I
** Note: this is a combined Theory Group/LMA seminar (feb 4/5) *
The seminars will provide a guide to contemporary understanding of star formation, outlining current theory and the observations that motivate it. A conception of star formation has emerged in which turbulence plays a dual role, both creating overdensities to initiate gravitational contraction or collapse, and countering the effects of gravity in these overdense regions. The key dynamical processes involved in star formation -- turbulence, magnetic fields, and self-gravity -- are highly nonlinear and multidimensional. Physical arguments are used to identify and explain the features and scalings involved in star formation, and results from numerical simulations are used to quantify these effects. After a discussion of basic physical processes, star formation on small scales and large scales will be reviewed in turn. The issues covered will include how cores form and evolve within giant molecular clouds (GMCs), and how GMCs themselves form and evolve within spiral galaxies. Important problems includes what determines the initial mass function of stars, and what determines the overall star formation rate. Although outstanding questions remain, the framework is now in place to build a comprehensive theory of star formation.
The talks will be based on my 2007 ARAA review with Chris McKee.
A link to the ADS listing of the paper is available at:
http://adsabs.harvard.edu/abs/2007ARA%26A..45..565M
Also, since ARAA does not include tables of contents this is available at:
http://www.astro.umd.edu/~ostriker/publications/MO2007_TOC.pdf
Date: Tuesday 5-feb-2008
Speaker: Prof. Eve Ostriker (Univ. of Maryland)
Title: An Overview of "Theory of Star Formation" - Part II
** Note: this is a combined Theory Group/LMA seminar (feb 4/5) *
The seminars will provide a guide to contemporary understanding of star formation, outlining current theory and the observations that motivate it. A conception of star formation has emerged in which turbulence plays a dual role, both creating overdensities to initiate gravitational contraction or collapse, and countering the effects of gravity in these overdense regions. The key dynamical processes involved in star formation -- turbulence, magnetic fields, and self-gravity -- are highly nonlinear and multidimensional. Physical arguments are used to identify and explain the features and scalings involved in star formation, and results from numerical simulations are used to quantify these effects. After a discussion of basic physical processes, star formation on small scales and large scales will be reviewed in turn. The issues covered will include how cores form and evolve within giant molecular clouds (GMCs), and how GMCs themselves form and evolve within spiral galaxies. Important problems includes what determines the initial mass function of stars, and what determines the overall star formation rate. Although outstanding questions remain, the framework is now in place to build a comprehensive theory of star formation.
The talks will be based on my 2007 ARAA review with Chris McKee.
A link to the ADS listing of the paper is available at:
http://adsabs.harvard.edu/abs/2007ARA%26A..45..565M
Also, since ARAA does not include tables of contents this is available at:
http://www.astro.umd.edu/~ostriker/publications/MO2007_TOC.pdf
Date: Monday 25-Feb-2008
Speaker: Rachel Dudik (George Mason University)
Title: A Spitzer Spectroscopic and Chandra Imaging Survey of IR-bright LINERs: An Unexplored Frontier
With the recent discovery that virtually all local galaxies harbor massive nuclear black holes, there is now convincing evidence that active galactic nuclei (AGN) and normal galaxies in our local Universe are fundamentally connected. However, the nature of this connection and the detailed evolutionary history connecting these objects is unknown. Low Ionization Nuclear Emission Line Regions (LINERs), defined by their narrow optical emission lines of low ionizatation uncharacteristic of photoionization by normal stars, may constitute a vital piece of this puzzle, possibly representing the "missing link" between the powerful quintessential AGN in the Universe and galaxies such as our own. However, despite several decades of research, there are still open questions including what fraction of LINERs are truly AGN. Virtually all previous extensive multi-wavelength studies of LINER galaxies have been carried out on optically-selected samples. However, these studies systematically exclude the IR-bright population, which constitutes approximately 80% of all nearby LINERs. What is the ionization mechanism responsible for the emission line spectra in these objects? How do LINERs fit into the overall scheme of galaxies as we know it? What is the evolutionary connection between inactive star forming galaxies and AGNs? In this talk, I will summarize recent results from our ongoing infrared spectroscopic survey of LINERs.
Date: Monday 3-Mar-2008
Speaker: Johannes Staguhn (Goddard)
Title: "First Results from Astronomical Observations with the GISMO 2 Millimeter Bolometer Camera at the IRAM 30m Telescope"
The 2mm bolometer camera GISMO (Goddard-IRAM Superconducting 2-Millimeter Observer) was installed for the first time in November 2007 at the IRAM 30m telescope on Pico Veleta in Spain. With its 128 pixel superconducting transition edge sensor bolometer array, this instrument provides unprecedented observational capabilities in terms of its field of view and sensitivity in the 2mm atmospheric window. In particular, observations of dust-enshrouded massive starburst galaxies and quasars can be performed very efficiently with the instrument even at redshifts of z>7. Furthermore GISMO provides important complementary data to observations obtained with other (sub-)millimeter instruments, such as SHARC-2 (350um), SCUBA, (450 and 850 um), AzTEC (1.1 mm), and MAMBO (1.2 mm).
I will present preliminary astronomical results obtained during its commissioning observing period, and discuss scientific capabilities that we can expect from the instrument in the future.
Date: Thursday 13-Mar-2008
Speaker: Bengt-Göran Andersson
Title: Observational Evidence for Interstellar Radiative Grain Alignment
Magnetic fields are expected to play a crucial role in the dynamics of the ISM, but are notoriously difficult, and usually telescope-costly, to measure in quantitative ways. The observationally easiest way of tracing the magnetic field, at moderate extinction, is through the used of optical/NIR polarimery of background stars (and the corresponding use of polarized FIR emission for cloud cores). This polarization is generally agreed to be caused by dichroic extinction (emission) due to asymmetric dust grains aligned by the magnetic field. Using the statistical Chandrasekhar-Fermi (CF) method, such data also allows the field strength to be estimated. The interpretation of the polarimetry is, however, hampered by the lack of a detailed understanding of the grain alignment physics. Major theoretical advances over the last couple of decades have ? until recently ? not been matched by similar observational progress. I will discuss new multi-wavelength optical/NIR polarimetry, supported by optical, NIR and FIR photometry, which provides observational support for radiation driven grain alignment, but also yields some surprises. I will show that cloud geometry and the presence of hot stars - nearby to, and embedded in, the clouds ? can significantly affect the results and have to be taken into account in the data analysis. In addition to providing empirical evidence for the dominant alignment mechanism, this kind of data will allow us to constrain and study secondary alignment and disalignment mechanisms.
Date: Monday 31-Mar-2008
Speaker: Hiroshi Koyama (University of Maryland)
Title: TBA
Date: Monday 31-Mar-2008
Speaker: Hiroshi Koyama (University of Maryland)
Title: Numerical Modeling for Galactic ISM and Star Formation
We have developed the numerical model for galactic ISM and star formation feedback due to HII regions. The self- gravitating, multiphase gas disk is simulated in a two- dimensional local shearing periodic box. Our simulations resolve formation and destruction of GMCs. We studied various statistics of GMCs such as velocity dispersion, Toomre's Q value, star formation rate, etc. In my talk, similarity and diversity of the GMCs are presented and discussed.
Date: Tuesday 15-Apr-2008
Speaker: Edmund Hodges-Kluck (University of Maryland)
Title: "Dense, Parsec-Scale Molecular Clumps near the Great Annihilator"
We report on CARMA data near the Galactic center towards the Great Annihilator black hole candidate. We see over ten dense molecular clumps with n > 10^5 cm^-3, and argue that the densities and size scales support the idea that atomic gas near the Galactic center shocks, forms molecular clouds, and falls deeper into the potential to end up in the region of the Sgr GMCs.
Date: Tuesday 22-Apr-2008
Speaker: Lisa Wei (University of Maryland) and Misty LaVigne (University of Maryland)
Title: Understanding the Blue-sequence E/S0 Populations: Fading Remnants and Future Spirals and An Overview of Feathers with Preliminary CARMA Results
Order of speakers to be determined by shotgun method.
Date: Tuesday 29-April-2008
Speaker: Claudia Knez (University of Maryland)
Title: Chemical Evolution of Ice and Gas from Molecular Clouds to Protostars
Date: Thursday 15-May-2008
Speaker: Tony Wong (University of Illinois, Urbana-Champaign)
Title: Atomic and Molecular Gas in the Large Magellanic Cloud
We examine the conditions for detection of CO(1-0) emission in the Large Magellanic Cloud (LMC), using the recently competed second NANTEN CO survey. In particular, we investigate correlations between CO and HI peak brightness temperature, integrated intensity, and line width. We find that significant HI column density is a necessary but not sufficient condition for CO detection, with many regions of bright HI emission not associated with molecular clouds. This conclusion remains unchanged even when isolating the component of HI most closely matched to the CO velocity using a Gaussian decomposition, since in most cases this yields the dominant HI component. HI linewidth appears not to influence the likelihood of CO detection. This suggests that if colliding flows in the atomic medium lead to the formation of giant molecular clouds (GMCs), the turbulent energy must dissipate before CO becomes detectable.
